Current coastal protection strategy in Portugal defines beach and shoreface nourishment as a vali... more Current coastal protection strategy in Portugal defines beach and shoreface nourishment as a valid measure to mitigate coastal erosion in some erosional hot-spots, being considered as an adaptation measure under the present climate change scenario, including the impacts of sea level rise. However, scant objective data on shoreface nourishments are available to evaluate performance of this type of intervention in mitigating beach erosion and managing coast risk. We present the first monitoring results of a ≈2.4 × 106 m3 shoreface nourishment on the Aveiro coast (Costa Nova—Ílhavo), the largest until now in Portugal, focusing on its morphological development, impacts on adjacent beaches due to alongshore spreading and cross-shore redistribution, and contribution to the sediment budget of the nourished sediment cell. The analyses are based on high-resolution coastal monitoring data, provided by the Portuguese COaStal MOnitoring Program (COSMO). A Multiple Monitoring Cell (MMC) approach...
The ongoing rise in sea level affects tidal propagation and circulation in estuaries, and these c... more The ongoing rise in sea level affects tidal propagation and circulation in estuaries, and these changes can have far reaching consequences on the sediment dynamics, water quality and extreme water levels. This study aims at anticipating the evolution of the tidal dynamics in the Tagus (Portuga l) in the 21 st century, in particular due to sea level rise (SLR). The existence of a resonance mode of about 8 hours in this estuary, that selectively amplifies both semi -diurnal and quarter -diurnal tidal constit u- ents, makes the response of the Tagus estu ary to SLR unique. The study was conducted with a shallow water model, forced by present and future conditions, namely higher mean sea levels and an extrapolated bathymetry based on present sedimentation rates. Model results showed that SLR will significan tly affect tidal asymmetry, in particular because the intertidal area can decrease by up to 40% by the end of the 21 st century. As a result, the strong ebb -dominance of this estuar...
The breaking wave height is a crucial parameter for coastal studies but direct measurements const... more The breaking wave height is a crucial parameter for coastal studies but direct measurements constitute a difficult task due to logistical and technical constraints. This paper presents two new practical methods for estimating the breaking wave height from digital images collected by shore-based video monitoring systems. Both methods use time-exposure (Timex) images and exploit the cross-shore length ( L H s ) of the typical time-averaged signature of breaking wave foam. The first method ( H s b , v ) combines L H s and a series of video-derived parameters with the beach profile elevation to obtain the breaking wave height through an empirical formulation. The second method ( H s b , v 24 ) is based on the empirical finding that L H s can be associated with the local water depth at breaking, thus it can be used to estimate the breaking wave height without the requirement of local bathymetry. Both methods were applied and verified against field data collected at the Portuguese Atlanti...
Coastal video monitoring has been proven to be a valuable shore-based remote-sensing technique to... more Coastal video monitoring has been proven to be a valuable shore-based remote-sensing technique to study coastal processes, as it offers the possibility of high-frequency, continuous and autonomous observations of the coastal area. However, the installation of a video systems infrastructure requires economical and technical efforts, along with being often limited by logistical constraints. This study presents methodological approaches to exploit “surfcam” internet streamed images for quantitative scientific studies. Two different methodologies to collect the required ground control points (GCPs), both during fieldwork and using web tools freely available are presented, in order to establish a rigorous geometric connection between terrestrial and image spaces. The application of an image projector tool allowed the estimation of the unknown camera parameters necessary to georectify the online streamed images. Three photogrammetric procedures are shown, distinct both in the design of th...
Regional/global-scale information on coastline rates of change and trends is extremely valuable, ... more Regional/global-scale information on coastline rates of change and trends is extremely valuable, but national-scale studies are scarce. A widely accepted standardized methodology for analysing long-term coastline change has been difficult to achieve, but is essential to conduct an integrated and holistic approach to coastline evolution and hence support coastal management actions. Additionally, databases providing knowledge on coastline evolution are of key importance to support both coastal management experts and users. <br><br> The main objective of this work is to present the first systematic, global and consistent long-term coastline evolution data of Portuguese mainland low-lying sandy. <br><br> The methodology used quantifies coastline evolution using an unique and robust coastline indicator (the foredune toe), which is independent of short-term changes. <br><br> The dataset presented comprises: 1) two polyline sets, mapping the 1958 and 201...
Sediment grain size variability is fundamental to understand the processes and direction of sedim... more Sediment grain size variability is fundamental to understand the processes and direction of sediment transport on littoral systems. The aim of this work is the characterization of the grain size variability and the implications on the definition of adequate sampling strategies. The work was developed at Norte beach, a high energetic and heterometric sandy beach located at Nazaré (west coast of Portugal). The beach sediment was digitally photographed in order to compute the median grain size using the image analysis based on the autocorrelation method. A total of 1498 images were taken covering the beach face superficial and subsuperficial sediment and also some beach face representative cores. Results question the representativeness of superficial sampling as systematic deviation from the beach “typical” grain size was detected.
Headland sediment bypassing plays a major role in definition of coastal sedimentary budget and co... more Headland sediment bypassing plays a major role in definition of coastal sedimentary budget and consequently in coastal management. This process is particularity important at headland-bay beaches on rocky coasts. However, headland-bay beach research is usually focused on the beach rotation since these beaches are generally regarded as closed systems. The sediment bypassing mechanisms have been extensively studied in the context of artificial structures (e.g. groins and jetties) but studies of natural headland sediment bypassing are scarce and usually applied to decadal time scales. This work aims to contribute to the understanding of headland sediment bypassing processes in non-artificial environments, taking as a case study a natural coastal stretch at the Portuguese west coast. The study is supported on the analysis of planform beach changes using Landsat satellite images (with an acquisition frequency of 16 days) complemented with field surveys with DGPS-RTK and ground-based photo...
Resumo: Está em curso, desde o início de 2011, um programa de amostragem de alta frequência em pr... more Resumo: Está em curso, desde o início de 2011, um programa de amostragem de alta frequência em praias representativas do troço litoral sob jurisdição da Administração da Região Hidrográfica do Tejo, no âmbito do projecto para a criação e implementação de um sistema de monitorização no litoral na área de jurisdição daquela entidade. A aquisição de dados inclui topografia, sedimentos, e registos fotográficos, elementos que permitirão analisar a evolução morfodinâmica daquele troço litoral à escala sazonal, anual e de longo-termo. O conjunto de dados geográficos originado será centralizado, gerido e disponibilizado através de uma plataforma Web SIG. A definição de valores de referência para indicadores de diagnóstico do estado das praias, nortearão a concepção de um programa de monitorização à escala regional que constituirá uma ferramenta de apoio ao nível do planeamento e gestão, que suportará técnica e cientificamente a tomada de decisão relativamente aos usos e ocupação da zona cos...
Current coastal protection strategy in Portugal defines beach and shoreface nourishment as a vali... more Current coastal protection strategy in Portugal defines beach and shoreface nourishment as a valid measure to mitigate coastal erosion in some erosional hot-spots, being considered as an adaptation measure under the present climate change scenario, including the impacts of sea level rise. However, scant objective data on shoreface nourishments are available to evaluate performance of this type of intervention in mitigating beach erosion and managing coast risk. We present the first monitoring results of a ≈2.4 × 106 m3 shoreface nourishment on the Aveiro coast (Costa Nova—Ílhavo), the largest until now in Portugal, focusing on its morphological development, impacts on adjacent beaches due to alongshore spreading and cross-shore redistribution, and contribution to the sediment budget of the nourished sediment cell. The analyses are based on high-resolution coastal monitoring data, provided by the Portuguese COaStal MOnitoring Program (COSMO). A Multiple Monitoring Cell (MMC) approach...
The ongoing rise in sea level affects tidal propagation and circulation in estuaries, and these c... more The ongoing rise in sea level affects tidal propagation and circulation in estuaries, and these changes can have far reaching consequences on the sediment dynamics, water quality and extreme water levels. This study aims at anticipating the evolution of the tidal dynamics in the Tagus (Portuga l) in the 21 st century, in particular due to sea level rise (SLR). The existence of a resonance mode of about 8 hours in this estuary, that selectively amplifies both semi -diurnal and quarter -diurnal tidal constit u- ents, makes the response of the Tagus estu ary to SLR unique. The study was conducted with a shallow water model, forced by present and future conditions, namely higher mean sea levels and an extrapolated bathymetry based on present sedimentation rates. Model results showed that SLR will significan tly affect tidal asymmetry, in particular because the intertidal area can decrease by up to 40% by the end of the 21 st century. As a result, the strong ebb -dominance of this estuar...
The breaking wave height is a crucial parameter for coastal studies but direct measurements const... more The breaking wave height is a crucial parameter for coastal studies but direct measurements constitute a difficult task due to logistical and technical constraints. This paper presents two new practical methods for estimating the breaking wave height from digital images collected by shore-based video monitoring systems. Both methods use time-exposure (Timex) images and exploit the cross-shore length ( L H s ) of the typical time-averaged signature of breaking wave foam. The first method ( H s b , v ) combines L H s and a series of video-derived parameters with the beach profile elevation to obtain the breaking wave height through an empirical formulation. The second method ( H s b , v 24 ) is based on the empirical finding that L H s can be associated with the local water depth at breaking, thus it can be used to estimate the breaking wave height without the requirement of local bathymetry. Both methods were applied and verified against field data collected at the Portuguese Atlanti...
Coastal video monitoring has been proven to be a valuable shore-based remote-sensing technique to... more Coastal video monitoring has been proven to be a valuable shore-based remote-sensing technique to study coastal processes, as it offers the possibility of high-frequency, continuous and autonomous observations of the coastal area. However, the installation of a video systems infrastructure requires economical and technical efforts, along with being often limited by logistical constraints. This study presents methodological approaches to exploit “surfcam” internet streamed images for quantitative scientific studies. Two different methodologies to collect the required ground control points (GCPs), both during fieldwork and using web tools freely available are presented, in order to establish a rigorous geometric connection between terrestrial and image spaces. The application of an image projector tool allowed the estimation of the unknown camera parameters necessary to georectify the online streamed images. Three photogrammetric procedures are shown, distinct both in the design of th...
Regional/global-scale information on coastline rates of change and trends is extremely valuable, ... more Regional/global-scale information on coastline rates of change and trends is extremely valuable, but national-scale studies are scarce. A widely accepted standardized methodology for analysing long-term coastline change has been difficult to achieve, but is essential to conduct an integrated and holistic approach to coastline evolution and hence support coastal management actions. Additionally, databases providing knowledge on coastline evolution are of key importance to support both coastal management experts and users. <br><br> The main objective of this work is to present the first systematic, global and consistent long-term coastline evolution data of Portuguese mainland low-lying sandy. <br><br> The methodology used quantifies coastline evolution using an unique and robust coastline indicator (the foredune toe), which is independent of short-term changes. <br><br> The dataset presented comprises: 1) two polyline sets, mapping the 1958 and 201...
Sediment grain size variability is fundamental to understand the processes and direction of sedim... more Sediment grain size variability is fundamental to understand the processes and direction of sediment transport on littoral systems. The aim of this work is the characterization of the grain size variability and the implications on the definition of adequate sampling strategies. The work was developed at Norte beach, a high energetic and heterometric sandy beach located at Nazaré (west coast of Portugal). The beach sediment was digitally photographed in order to compute the median grain size using the image analysis based on the autocorrelation method. A total of 1498 images were taken covering the beach face superficial and subsuperficial sediment and also some beach face representative cores. Results question the representativeness of superficial sampling as systematic deviation from the beach “typical” grain size was detected.
Headland sediment bypassing plays a major role in definition of coastal sedimentary budget and co... more Headland sediment bypassing plays a major role in definition of coastal sedimentary budget and consequently in coastal management. This process is particularity important at headland-bay beaches on rocky coasts. However, headland-bay beach research is usually focused on the beach rotation since these beaches are generally regarded as closed systems. The sediment bypassing mechanisms have been extensively studied in the context of artificial structures (e.g. groins and jetties) but studies of natural headland sediment bypassing are scarce and usually applied to decadal time scales. This work aims to contribute to the understanding of headland sediment bypassing processes in non-artificial environments, taking as a case study a natural coastal stretch at the Portuguese west coast. The study is supported on the analysis of planform beach changes using Landsat satellite images (with an acquisition frequency of 16 days) complemented with field surveys with DGPS-RTK and ground-based photo...
Resumo: Está em curso, desde o início de 2011, um programa de amostragem de alta frequência em pr... more Resumo: Está em curso, desde o início de 2011, um programa de amostragem de alta frequência em praias representativas do troço litoral sob jurisdição da Administração da Região Hidrográfica do Tejo, no âmbito do projecto para a criação e implementação de um sistema de monitorização no litoral na área de jurisdição daquela entidade. A aquisição de dados inclui topografia, sedimentos, e registos fotográficos, elementos que permitirão analisar a evolução morfodinâmica daquele troço litoral à escala sazonal, anual e de longo-termo. O conjunto de dados geográficos originado será centralizado, gerido e disponibilizado através de uma plataforma Web SIG. A definição de valores de referência para indicadores de diagnóstico do estado das praias, nortearão a concepção de um programa de monitorização à escala regional que constituirá uma ferramenta de apoio ao nível do planeamento e gestão, que suportará técnica e cientificamente a tomada de decisão relativamente aos usos e ocupação da zona cos...
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